Computer and network systems such as personal computers, workstations, server systems, and cloud storage systems, typically include data storage systems for storing and retrieving data. These data storage systems can include data storage devices, such as hard disk drives, solid state storage devices, tape storage devices, and other mass storage devices. To achieve a measure of reliability and availability, these data storage systems can include multiple data storage devices in various arrays and configurations. One such data storage system is a redundant array of independent disks (RAID) and can be configured in with different architectures to satisfy various capacity, reliability, and availability requirements.
In typical arrayed storage systems that incorporate more than one data storage device, when a single data storage device fails or shows signs of failure, the data stored on the failing data storage device can be transferred to another data storage device if the failing data storage device is still accessible. This transfer of data allows for a replacement data storage device to be prepared in advance to participate in the arrayed storage system. In alternate examples, a replacement data storage device is instead prepared from data included on other data storage devices, which might incorporate parity data used to reconstruct the data stored on the failing data storage device. However, the reconstruction process is slow and resource intensive. Thus, if the failing data storage device is still accessible during failure, then data can be transferred from the failing data storage device to the replacement data storage device, saving some of the time used in reconstruction of the data from other data storage devices.
However, transfer of data from the failing data storage device to the replacement data storage device can be time consuming and can expedite complete failure of the already failing data storage device. Moreover, many data storage devices include cache portions which include data that has not yet been written to storage portions of the data storage device. In rotating media data storage devices, such as hard disk drives, these cache portions can be included on the same rotating media as the storage portions. Accessing data from failing rotating media data storage devices thus can incur large seek penalties and access delays due to having to access data from both the cache portion and storage portion of the same rotating media.